A search-and-rescue operation has been launched in Wyoming's Wind River Range for Randy Udall, the younger brother of Sen. Mark Udall. The Colorado Democrat's brother, who had been hiking alone, started the trek on June 20 and was supposed to exit the mountains last week, the Denver Post reports. The 61-year-old, a well-known environmental advocate in Colorado, is an experienced hiker who has hiked in the area many times, the local sheriff's office says. (More Mark Udall stories.)